Syringe-ampoules are already known in the art, particularly those described in French Pat. No. 714108. These devices are comprised of an ampoule provided with a stopper encased by the open end of the ampoule, and associated with a rotatable valve traversed by an axial conduit, connected to a radial conduit designed to open into a cavity in communication with the interior of the ampoule. In the example illustrated in FIGS. 1 and 2 of this patent, the opening and closing of the valve are affected by the rotation of the needle carrier. The solution is not useful in practice, since the operator has only one hand available to hold the syringe and to activate the valve, his other hand being occupied holding the patient's skin.
The embodiment of FIG. 3 of this patent demonstrates one solution to this problem. However, the manufacture of the ampoule-syringe described is very costly and the product unsatisfactory in numerous respects. Actually, this construction entails a stopper which is in contact with the pharmaceutical substance or liquid medication contained in the ampoule, a rotatable valve contained in a central opening disposed in the stopper means and also in partial contact with the substance to be injected, a special needle-holding cap adapted to the stopper means and a spiral spring between the stopper and the cap.
The manufacture of a special needle and needle holder is a costly operation. The fact that the needle is mounted on a needle-holding tip at the time of assembly and especially at the time the ampoule is pressurized means that the pressurized gas to be introduced into the ampoule must be injected through the syringe, thereby necessitating a complicated mechanism to avoid damaging the needle. This could also be achieved by filling the ampoule in a pressurized room or container, but the operation is complicated and relatively costly. The pressurization of the pharmaceutical substance could be accomplished by injecting the gas through the needle holding tip, previously positioned, followed by soldering or gluing the needle. Manipulating the needle is costly because it necessitates the utmost precautions. It must be done under sterile conditions to exclude any contamination, particularly glue residue.
The pharmaceutical substance is in contact with three elements made of different materials, the ampoule, the stopper and the valve. Furthermore, water-tightness between the stopper and the valve is difficult to achieve unless the body of the valve is firmly attached to the interior of the stopper, thereby causing considerable pull which impedes retraction of the ampoule at the time of injection.
Maintaining the stopper in place necessitates use of an encasing ring. The elements comprising the stopper means for the ampoule are the following: a stopper, a valve situated in a cylindrical cavity of said stopper, an encasing ring, a needle holding cap, a spring and a needle. Manufacturing and assembling all these pieces is extremely costly. Furthermore, preparation of the syringe for use requires the following operations: filling the ampoule with the pharmaceutical substance, placing the stopper on the ampoule, affixing the stopper by means of the encasing ring, positioning the valve in the central opening of the stopper, positioning the spring, injecting compressed gas into the ampoule to pressurize the liquid and affixing the needle. These various preparatory phases are both delicate and costly. Further this kind of syringe does not permit aspiration of liquid, i.e. for checking presence of blood for intravenous injections or absence of blood for subcutaneous or intramuscular injections. Furthermore, it is known from the article which appears on page 17 of "Recipients en matiere plastique pour les preparations pharmaceutiques, essai et controle" ("Plastic Containers for Pharmaceuticals Preparations, Experimentations and Control"), published in 1974 by the World Health Organization, and authored by Jack Cooper, that composite containers are often susceptible to interaction of materials. In particular, there has been observed a migration of certain components of synthetic material into pharmaceutical substance contents. Interaction between the pharmaceutical substance contents and the container when the latter is made of a polymer may change the physical characteristics of the polymer and/or pharmacological characteristics of the pharmaceutical substance contents. Even if its characteristics are initially satisfactory, the changes which may occur as a result of the prolonged interaction oblige manufacturers to pay particular attention to stability during storage.
Many other prefilled ampoule-syringes are known, comprising an ampoule containing liquid medication under pressure and a stopper means which closes the ampoule until it is used. One document which particularly well illustrates a technique currently in use is British Pat. No. 13142 which describes a prefilled ampoule-syring stoppered by a water-airtight stopper designed to be pierced by a double needle, one end of which penetrates through the stopper to the interior of the ampoule and the other end of which is for injecting the pharmaceutical substance into the patient's body. Pressurization of such ampoule must take place automatically in a pressurized atmosphere because the stopper is effective in one direction only. The needle, which has a specialized shape, requires a special and relatively costly manufacturing process, as a standard needle cannot be used with this device. Finally, piercing an elastomer stopper with a double needle can cause migration of inert particles into the pharmaceutical substance and into the patient's body, thereby posing a real danger to the patient.
A fluid withdrawal device and container disclosed in U.S. Pat. No. 3,159,159 which can also be used as a prefilled syringe, comprises a valve system for dispensing a liquid medication which is maintained under pressure in an adequate ampoule. The valve system functions like a stopper during a storage phase and like a spring actuated valve during the injection phase. The construction is complicated and the liquid is in contact with at least three different materials. Like the French patent, this device does not allow aspiration where it is used as a prefilled syringe.
A fluid dispensing device disclosed in U.S. Pat. No. 4,479,801 comprises a syringe body having a first opening which can be closed by an axially movable stopper and a separate piston for pushing the liquid through the movable stopper to an injection needle. The movable stopper functions like a valve for closing a passageway during the storage phase and for opening the same during the injection phase. The ampoule has two openings and the liquid is in contact with at least three different materials. The present invention proposes to overcome the various foregoing disadvantages and to offer the health profession a useful instrument, easy to manipulate, of economical construction and providing the patient with the requisite hygiene and cleanliness.